The present invention relates to jet aircraft engines, and, in particular, to inlet guide vanes therein.
In the past, in cold weather operations, the formation of ice on static engine parts caused a problem when the ice broke off and caused damage to downstream engine parts such as compressor blades, etc. It is further known that ice buildup drastically reduces airfoil characteristics whether on static or dynamic parts. Thus there is a need to reduce or eliminate icy buildup on aircraft parts.
In the past, hot air bled from the engine was ducted through channels in the metal vanes. Other schemes to reduce or eliminate ice buildup on metal vanes included electric current applied through a resistive layer, mechanically induced vibrations, sonically induced vibrations, etc.
With the advent of lightweight engine systems, the use of composite materials in the vanes, for example, has produced several problems. Composite materials are not good heat conductors so the use of hot fluids whether gas or liquid are not as effective. Also the composite vanes are more subject to damage from foreign objects (FOD) than equivalent metal vanes.
Several solutions to this have been proposed such as electric heating using a metalized fabric in the surface of the composite vane, fluid heating through a system of capillary tubes under a composite surface, and applying an antifreeze solution through surface holes.
The use of capillary tubes in composite vanes requires that the tubes be within a few hundredths of an inch of the surface because of the poor heat conduction. The proximity of the tubes to the surface may reduce impact resistance to FOD resulting in replacement of the vanes from objects that would not otherwise damage the vane. The use of tubes produces a trade-off between the ability to de-ice and impact resistance to FOD.
Therefore, there is a need for a composite vane having the ability to de-ice and to prevent FOD damage as compared to the devices noted above.